U.S. patent number 6,145,984 [Application Number 09/218,886] was granted by the patent office on 2000-11-14 for color-enhancing polarized lens.
This patent grant is currently assigned to Maui Jim, Inc.. Invention is credited to Michael J. Farwig.
United States Patent |
6,145,984 |
Farwig |
November 14, 2000 |
Color-enhancing polarized lens
Abstract
A color-enhancing polarized lens is constructed having
substantially trichroic spectral-transmission. A lens so
constructed may have an overall transmitted tint which is a
virtually colorless gray to the eye. A lens so constructed and
tint-neutralized delivers unexpectedly dramatic improvements in the
areas of color saturation, chromatic and luminous contrast, clarity
of detail, depth perception, haze penetration, and overall
impact.
Inventors: |
Farwig; Michael J. (Lahaina,
HI) |
Assignee: |
Maui Jim, Inc. (Peoria,
IL)
|
Family
ID: |
26749253 |
Appl.
No.: |
09/218,886 |
Filed: |
December 22, 1998 |
Current U.S.
Class: |
351/49;
351/159.56; 351/159.66; 351/44 |
Current CPC
Class: |
G02C
7/104 (20130101); G02C 7/12 (20130101); G02C
7/102 (20130101); G02C 2202/16 (20130101) |
Current International
Class: |
G02C
7/10 (20060101); G02C 7/12 (20060101); G02C
7/00 (20060101); G02C 007/12 () |
Field of
Search: |
;351/44,49,163,165
;359/483,485,502,885 ;264/1.31,1.32,1.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
242 108 A1 |
|
Jan 1987 |
|
DE |
|
54-133149 |
|
Oct 1979 |
|
JP |
|
59-55403 |
|
Mar 1984 |
|
JP |
|
62-55621 |
|
Mar 1987 |
|
JP |
|
483697 |
|
May 1938 |
|
GB |
|
Other References
WW. Coblentz, et al., "Spectral Transmissive Properties and use of
Colored Eye-Protective Glasses", Circular of the National Bureau of
Standards C421, U.S. Department of Commerce, Jun. 1, 1938..
|
Primary Examiner: Mai; Huy
Attorney, Agent or Firm: McDonnell Boehnen Hulbert &
Berghoff
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
The priority benefit under 35 U.S.C. .sctn. 119(e) of provisional
patent application Ser. No. 60/068,697 filed Dec. 23, 1997, is
claimed.
Claims
What is claimed is:
1. A lens comprising a front lens element and a rear lens
element,
each said lens element having a convex surface on one side and
concave surface on the other side thereof,
at least one of said lens elements comprising a trichroic contrast
enhancer,
said lens elements being adhered together with a light-polarizer
disposed between said lens elements,
front and rear exterior surfaces of said lens being defined by said
convex surface of said front lens element and said concave surface
of said rear lens element, respectively, and
said trichroic contrast enhancer:
a) providing maximum light transmission with respect to CIE
illuminant C at three or more points (hereinafter "maxima"), at
least one of said maxima being located within each of three
maximum-transmission wavelength bands defined by respective
spectral ranges of 610-650 nm, 480-520 nm, and 420-460 nm, each of
said maxima having a light transmission value at least 125% of the
integrated visible-light transmission value of said trichroic
contrast enhancer, b) providing minimum light transmission with
respect to CIE illuminant C at two or more points (hereinafter
"minima"), at least one of said minima being within each of two
minimum-transmission wavelength bands defined by spectral ranges
located chromatically between the spectral ranges defining said
maxima,
wherein the value of the highest of said maxima in each of said
maximum-transmission bands is equal to 80% to 120% of the average
value of the three highest of said maxima, and
wherein the lowest value of said minima in each of said
minimum-transmission bands is 75% or less of the value of the
integrated visible-light transmission value of said lens.
2. The lens of claim 1 wherein the front lens element is
photochromic.
3. The lens of claim 1 having an antireflectant coating on at least
one exterior surface of said lens.
4. The lens of claim 1 having a hydrophobic coating on at least one
surface of said lens.
5. The lens of claim 1 having a semi-transparent mirror coating on
said convex surface of said front lens element.
6. The lens of claim 5 having a hydrophobic coating applied over
said semi-transparent mirror coating.
7. The lens of claim 1 having a semi-transparent mirror coating on
said concave surface of said front lens element.
8. The lens of claim 1 having a tint-neutralizing filter in
addition to said trichroic contrast enhancer, said
tint-neutralizing filter cooperating with said trichroic contrast
enhancer to cause the transmitted tint of said lens to appear
substantially neutral-gray under sunlight.
9. The lens of claim 8 wherein said filter is selected from the
group consisting of glass dopants, plastic additives, dyes, stains,
heat treatments, exposure to ultraviolet light, chemical baths,
semi-transparent mirror coatings, and semi-transparent color
coatings.
10. A lens comprising at least one lens element and a
light-polarizer, said lens having a convex exterior surface on one
side thereof and a concave exterior surface on another side
thereof, said lens providing the following trichroic transmission
characteristics:
a) maximum light transmission with respect to CIE illuminant C at
three or more points (hereinafter "maxima"), at least one of said
maxima being located within each of three maximum-transmission
wavelength bands defined by respective spectral ranges of 610-650
nm, 480-520 nm, and 420-460 nm, each of said maxima having a light
transmission value at least 125% of the integrated visible-light
transmission value of said trichroic contrast enhancer,
b) minimum light transmission with respect to CIE illuminant C at
two or more points (hereinafter "minima"), at least one of said
minima being within each of two minimum-transmission wavelength
bands defined by spectral ranges located chromatically between the
spectral ranges defining said maxima,
wherein the value of the highest of said maxima in each of said
maximum-transmission bands is equal to 80% to 120% of the average
value of the three highest of said maxima, and
wherein the lowest value of said minima in each of said
minimum-transmission bands is 75% or less of the value of the
integrated visible-light transmission value of said lens.
11. The lens of claim 10 having an antireflectant coating on at
least one exterior surface of said lens.
12. The lens of claim 10 having a hydrophobic coating on at least
one said exterior surface of said lens.
13. The lens of claim 10 having a semi-transparent mirror coating
on said convex surface of said lens.
14. The lens of claim 10 having a front lens element and a rear
lens element,
each said lens element having a convex surface on one side and
concave surface on the other side thereof,
said lens elements being adhered together with a light-polarizer
disposed between said lens elements,
front and rear exterior surfaces of said lens being defined by said
convex surface of said front lens element and said concave surface
of said rear lens element, respectively, and,
said lens further comprising a semi-transparent mirror coating on
said concave surface of said front lens element.
15. The lens of claim 10 having a spectral filter in addition to
said trichroic transmission providing element, said spectral filter
cooperating with said trichroic transmission providing element so
as to cause the transmitted tint of said lens to appear
substantially neutral-gray in daylight conditions.
16. The lens of claim 15 wherein said spectral filter is selected
from the group consisting of class dopants, plastic additives,
dyes, stains, heat treatments, exposure to ultraviolet light,
chemical baths, semi-transparent mirror coatings, and
semi-transparent color coatings.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the sciences of optics and human color
perception in general and to the field of sunglass lenses in
particular. More specifically, the invention relates to the
application of optical polarization, trichroic spectral-filter
technology, and the principles of human color perception, to
produce sunglass lenses of unprecedented vision-enhancing
capability.
2. Description of Related Technology
The principal benefit of wearing sunglasses is obvious. They
provide comfort and protection for the eyes by attenuating
excessively bright light. Virtually all modern sunglasses further
protect the eyes by filtering out harmful but invisible ultraviolet
light. Some of these also provide increased eye comfort by blocking
infrared light, which can aggravate "dry-eye" and cause ocular
discomfort--particularly among contact-lens wearers. Neutral-gray
remains the most popular tint, with 10 to 20 percent luminous
transmission being most common.
Some sunglasses operate on the principle of aggressively blocking
certain portions of the visible spectrum: an example of these are
the blue-blocking amber types. These feature high transmission of
yellow, orange, and red, diminished transmission of green and
blue-green, and virtually no transmission of blue and violet. Color
values are highly distorted by lenses of this type, and despite
acceptance of amber to enhance contrast, loss of chromatic contrast
results as their deep yellow-orange tint weakens color
differentiation.
Prior art amber lenses are often claimed to increase visual acuity
by limiting transmission to the red half of the spectrum, thus
reducing chromatic aberration inherent in human vision. By blocking
short visible wavelengths--roughly those below 500 nm--which
scatter readily in the atmosphere and are more difficult for the
human eye to focus, the deeper shades of amber tints are said to
increase the visibility of distant objects or those obscured by fog
or haze. The prior art advocates blocking blue spectra (380-500 nm)
while promoting yellow spectra (570-600 nm) to maximize visual
acuity, especially in hazy or foggy conditions.
Polarized glasses reduce glare by blocking light which has become
polarized by being reflected off various surfaces. This is
accomplished by means well known to the art. Polarized light
reflected off horizontal surfaces--and to a lesser degree, diagonal
surfaces--can be blocked by polarized sunglasses. This improves
visibility of the surface itself, and in the case of water and
other transparent media, increased visibility beneath the surface.
By removing blinding reflected glare, and the need to squint when
facing it, polarized lenses also provide increased eye safety and
comfort for the wearer.
In the past, the benefits of polarization as applied to sunglasses
have been well known and exploited. Indeed there are many existing
commercial examples of polarized sunglasses. These have been
available in both plastic and glass lens constructions for decades.
And while the neutral-tint polarized sunglasses of prior art can
remove reflected glare quite effectively--thereby revealing
previously-hidden color--they produce no further enhancements to
color saturation or contrast beyond this "unveiling" effect.
Various colored polarized sunglass lenses are also available; these
suffer from the same shortcomings and compromises found in all
colored sunglass lenses of prior art--they all favor some colors at
the expense of others. Sunglass lenses of prior art, polarized or
not, which were intended to enhance vision by means of non-neutral
(i.e., colored) tint exhibit intrinsic chromatic inaccuracy. Amber
lenses weaken blue, rose lenses weaken green, green lenses weaken
red, and so on. Ordinary gray lenses often weaken colors and
contrast.
Each tint has particular advantages in particular circumstances but
none has all. Tint selection has been determined in the past by
user preference, and with regard to particular landscapes, seasons,
and subjects viewed. The prior art has failed to combine into a
single pair of sunglasses all the desirable characteristics and
none of the unwanted compromises of the many known lens types and
tints. In the sunglass industry a long-standing and unfulfilled
need has existed for a lens which simultaneously provides: a)
excellent glare reduction, b) enhanced color saturation, chromatic
contrast, luminous contrast, and acuity, c) apparently neutral
tint; d) high color fidelity; e) improved visibility or colored
objects partially obscured by fog or haze; and f) complete UV
protection. It would be desirable to provide all of these qualities
simultaneously and, highly preferably, without compromise.
SUMMARY OF THE INVENTION
Accordingly, the invention provides the sunglass user with improved
perceptions of color saturation and optical contrast without
requiring any apparent coloration (except gray) in the transmitted
tint, promoting a sense of heightened accuracy and differentiation
in viewed colors while providing full protection from UV and
shortwave-blue spectra. Further, the lenses of the invention
provide increased visual acuity, and maximize the visibility of
objects partially obscured by fog or atmospheric haze.
A polarized sunglass lens having certain trichroic
spectral-transmission properties as defined herein achieves one or
more of these objects. The term "trichroic" denotes tricolor
transmission--i.e., favoring the transmission of three distinct
colors--in this case, the primary additive colors red, green, and
blue. When viewing colorful subjects under clear bright sunlight,
there is an unexpected and profound synergism in the lens of the
present invention. The polarizer increases the color-enhancing
effects of trichroic transmission. It is believed that the
polarizer, through its revealing of color previously-hidden by
reflected glare, uniquely cooperates with the trichroic contrast
enhance to provide increased effectiveness.
The lens of one embodiment of the invention includes two lens
elements, at least one element having trichroic properties as
defined herein, laminated together with a polarizing film enclosed
within. Alternative embodiments may incorporate polarized plastic
lenses dyed, coated, or otherwise treated to have the said
trichroic properties.
Other forms of the invention may include single-element trichroic
lenses having a polarizing coating or surface treatment. Moreover,
lenses of self-polarized synthetically-grown crystal similar to
natural iolite or cordierite may have dopants added/or surface
coatings applied to achieve trichroic properties. Many embodiments
are possible; it is intended that the scope of the present
invention include all implicit variations and functional
equivalents as well as those examples herein stated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a lens of the invention,
depicting a polarizing film disposed between two curved lens
elements, wherein the front lens element is photochromic, the rear
lens element is a trichroic contrast enhancer, and coatings are
applied to the convex surface of the front lens element and to the
concave surface of the rear lens element.
FIG. 2 is a cross-sectional view of another embodiment of a lens of
the invention, depicting a polarizing film disposed between two
curved lens elements, wherein the front lens element is
photochromic, the rear lens element is a trichroic contrast
enhancer, and coatings are applied to the concave and convex
surfaces of the front lens element and to the concave surface of
the rear lens element.
FIG. 3 is a cross-sectional view of an uncoated lens of another
embodiment of the invention, depicting a polarizing film disposed
between two curved lens elements, wherein at least one of said lens
elements is a trichroic contrast enhancer.
FIG. 4 is a cross-sectional view of another embodiment of a lens of
the invention, depicting a curved lens body which is a trichroic
contrast enhancer, and which has coatings applied to its concave
and convex surfaces, at least one of said coatings being a
polarizer.
DETAILED DESCRIPTION OF THE INVENTION
It has been found that polarized sunglass lenses having trichroic
properties as defined herein can provide unexpectedly significant
enhancements to human vision with respect to color saturation,
chromatic and luminous contrast, clarity of detail, depth
perception, haze penetration, and overall visual impact.
As used herein, "photochromic" is defined as having the property of
darkening (minimizing light transmittance) when exposed to
sunlight, and lightening (maximizing light transmittance) when not
exposed to sunlight.
As used herein, "trichroic contrast enhancer" shall be defined as
any spectral filter which
a) provides maximum transmission with respect to CIE (Commission
Internationale De L'Eclairage) illuminant C at three or more points
(hereinafter "maxima"), at least one of said maxima being located
within each of three maximum-transmission wavelength bands, one
each of said maximum-transmission wavelength bands being within the
spectral ranges of 610-650 nm, 480-520 nm, or 420-460 nm (red,
green, and blue respectively), each of said maxima having a value
at least 125% of the integrated visible-light transmission of the
spectral filter means;
b) provides minimum transmission with respect to CE illuminant C at
two or more points (hereinafter "minima"), at least one of said
minima being located within each of two minimum-transmission
wavelength bands, within the spectra located chromatically between
the maximum-transmission bands;
c) wherein the value of the highest of the maxima in each of the
aforesaid maximum-transmission bands is equal to 80% to 120% of the
average value of the three highest of the said maxima; and
d) wherein the lowest value of the minima in each of the
minimum-transmission bands is no greater than 75% of the value of
the integrated visible-light transmission of the spectral filter
means.
The trichroic property referred to herein is not to be confused
with the trichroic category of naturally-polarized pleochroic
crystals found in nature, such as iolite, cordierite, and the like.
The trichroism of these crystals is directional in nature, as it is
related to the planes of polarization intrinsic to the crystal, and
thus the crystal will be seen to change color as it is rotated. The
intrinsic polarizing property of this category of crystals was
exploited by Rogers (U.S. Pat. No. 3,617,114). The trichroism
utilized in the invention is not of the nature of Rogers, although
the polarizing means of the present invention could be extended to
include such crystals for their polarizing properties, when used in
conjunction with a trichroic contrast enhancer of the invention.
This usage could involve growing the crystal synthetically, adding
dopants to substantially achieve the non-directional trichroic
spectral transmission of the invention.
The invention is distinguishable from the prior art at least by
advocating a lens which appears to be neutral-gray, but which
enhances color and contrast. The invention is distinguishable from
the existing notion of blocking all blue spectra to heighten visual
acuity, advocating instead the balanced attenuation of blue
wavelengths and of blue's complement, amber-yellow. Instead of
relying on the simple broadband-tint technology of the prior art,
the invention uses complex narrowband filtering. The invention
exploits previously unknown levels of vision-enhancement, realized
only when polarization is combined with balanced RGB
trichroism.
It is intended that all polarized lenses incorporating material or
treatments having trichroic properties as defined herein be
considered to be within the scope of the invention.
For the purposes of the invention, any finished lens, lens element,
lens layer, lens construction, or treatment thereof meeting the
above criteria is considered to be "trichroic"; that is, providing
maximum visible-light transmission in three discrete spectral
bands, with attenuated spectral bands therebetween, as defined
above. An example of an ophthalmic mineral glass meeting all of the
above criteria is product code S-8807, from Schott Glass
Technologies Incorporated of Duryea, Pa.
Schott S-8807 glass exhibits the characteristic chameleon-like
property of all true trichroics; it has a peculiar amethyst tint
which, in the case of Schott S-8807 glass, appears blue-violet in
sunlight, rose in incandescent light, and green in fluorescent
light. Trichroic lens material of a tint other than amethyst could
be used in the invention, such as Schott S-8801 glass, which is
bluish in daylight. Trichroic material of any color could be used
as long as the overall transmitted tint of the finished lens can be
made satisfactory through the incorporation of additional tint.
Trichroic lens material of neutral-gray tint would be especially
desirable for the sake of simplicity. Trichroic neutral-gray glass
has been reduced to practice and at the time of this writing is
being incorporated into finished lenses for evaluation. The
experimental glass, Schott S-8506 glass, is formed of a lanthanide
base composition doped with oxides of neodymium (Nd), praseodymium
(Pr), and erbium (Er). The dopant ratio chosen produces a glass
which is neutral gray in tint, has a luminous transmission of
approximately 61% at 1 mm thickness, and complies with spectral
transmission requirements of the European Committee for
Standardization (CEN) Standard EN 1836 of January 1997. The dopant
ratio consists of 1.512 mole percent Nd.sub.2 O.sub.3, 1.657 mole
percent Pr.sub.2 O.sub.3, and 1.243 mole percent Er.sub.2 O.sub.3,
in the same lanthanide base as Schott S-8807 glass but without the
oxides of copper and cerium which are present in Schott S-8807
glass.
As used herein, the phrase "lens elements" includes but is not
limited to lenses formed of ground and polished mineral glass,
crystal, or optical-grade plastic; molded and/or extruded plastic
lenses; and flat plastic which is cut and formed into lenses of a
desired shape.
In a preferred embodiment of the invention, there is provided a
laminated, light-polarizing lens constructed with a front lens
element and a rear lens element, each lens element has a convex
surface on one side and a concave surface on the other side,
wherein the front lens element is photochromic, and the rear lens
element is a trichroic contrast enhancer, wherein the lens elements
are adhered together with a polarizing film disposed between the
lens elements, the convex surface of the front lens element has a
semi-transparent mirror coating with a hydrophobic overcoating, and
the concave surface of the rear lens element has an antireflectant
coating with a hydrophobic overcoating.
In another embodiment of the invention, there is provided a
laminated light-polarizing lens constructed with a front lens
element and a rear lens element, each lens element has a convex
surface on one side and a concave surface on the other side, the
front lens element being photochromic and the rear lens element
being a trichroic contrast enhancer, wherein the lens elements are
adhered together with a polarizing film sandwiched between the lens
elements, the convex surface of the front lens element having a
hydrophobic coating, the concave surface of the front lens element
having a semi-transparent mirror coating, and the concave surface
of the rear lens element having an antireflectant coating with a
hydrophobic overcoating.
In another embodiment of the invention, there is provided a single
lens body which has a convex surface on one side and concave
surface on the other side, wherein the lens body is a trichroic
contrast enhancer with a polarizing coating or treatment applied to
at least one of its surfaces, and the lens body has an
antireflectant coating with a hydrophobic overcoating applied to
its concave surface.
Referring to FIG. 1, a preferred embodiment of the invention is
depicted as composite lens body generally designated 1 having a
front lens element 2 and a rear lens element 4, conjoined with and
enclosing a polarizing film 3, the front lens element being a brown
photochromic, the rear lens element being a trichroic contrast
enhancer, and the polarizing film being gray. The exact tints of
the front lens element and polarizing film, as well as any
treatments or coatings thereupon or therein can be chosen to
provide an apparently neutral transmitted tint.
For example, when using a 1 mm thick rear lens element of Schott
S-8807 glass, the pale purplish color of the glass (under CIE
standard illuminant C) can be rendered undetectable to the wearer
by using a common variety of slightly-bluish gray polarizer having
about 25% transmission, a 1 mm thick brown photochromic front lens
element of Photobrown TD from Corning Class in Corning, N.Y.,
coated with semi-transparent blue-lavender dielectric mirror
coating available as process 18S from North American Coating
Laboratories of Cleveland, Ohio (hereinafter "NACL").
Again referring to FIG. 1, a semi-transparent mirror coating 5 is
applied to the convex surface of the front lens element 2, a
hydrophobic silicon or amorphous diamond-like carbon (hereinafter
"DLC") coating 7 is applied over said semi-transparent mirror
coatings, an antireflectant coating 8 is applied to the concave
surface of the rear lens element 4, and a hydrophobic silicon
dioxide coating 9 is applied over the antireflectant coating 8. A
preferred method for the laminated-glass type of lens is to perform
all coatings prior to lamination to permit using the highest
practical annealing temperatures in the coating chamber. This
method imparts the best durability to the coatings.
Alternatively, the external surfaces of the composite lens may be
vacuum-coated after lamination if a process is used which maintains
a low enough temperature so as not to damage the polarizer or
lamination integrity. One such coating process is described in U.S.
Pat. No. 4,838,673. Another method currently available from a
number of coating vendors is an ion-assisted process originally
developed for plastic lenses. Ion-assisted coating can use chamber
temperatures low enough to be safe for laminated polarized glass
and plastic lenses.
The overall transmitted tint of the finished composite lens may be
rendered deliberately non-neutral if desired, by incorporating
additional tint(s) appropriate to the desired result, in a manner
similar to that used for neutralizing the composite tint. The
trichroism exaggerates otherwise subtle auxiliary tints, making it
easy to "swing" the tint in one chromatic direction or another
without introducing excessive density. The scope of the invention
is intended to include all such applications.
Antireflectant coatings reduce glare caused by reflections from
behind the wearer, or from the wearer's face. A preferred
multilayer broadband type is available from NACL, as well as from
many other optical coating vendors. The hydrophobic silicon dioxide
coating imparts a hydrophobic (water-repellant) and antistatic
(dust-repellant) property to the surface of the lens, making the
lens substantially easier to clean and to keep clean than lenses
not so coated. DLC coatings provide extreme scratch resistance with
hydrophobic/antistatic properties similar to silicon. Hydrophobic
silicon and DLC coatings have both been known in the sunglass
industry for some time, and are available from NACL as well as from
many other optical coating vendors. Alternatively, the silicon
coatings may be of the liquid-dip variety.
Referring to FIG. 2, an alternative embodiment is depicted as a
composite lens body generally designated 1, having a front lens
element 2 and a rear lens element 4; at least one of the lens
elements being a trichroic contrast enhancer, the lens elements 2
and 4 are conjoined with and enclose a polarizing film 3, and a
semi-transparent mirror coating 5 is applied to the concave surface
of the front lens element for ultimate durability, antireflectant
coatings 9 and 7 are applied to the convex surface of the front
lens element and to the concave surface of the rear leans element
respectively, and hydrophobic coatings 6 and 8 are applied over
said antireflectant coatings on the front and rear lens elements,
respectively. The antireflectant coating on the convex surface of
the front lens element reduces reflections between the internal
mirror and the lens-to-air interface.
Substitutions may be made provided that the luminous and spectral
transmission properties of the specified materials are adequately
duplicated. For example, the spectral transmission profile of the
above-specified mirror coating could be approximated by using a
brown photochromic and a slightly-greenish gray polarizer, or by
using a pale green non-photochromic front lens element and a pale
brown or amber polarizer, and/or by using color coatings, dyes, or
other treatments. It is intended that all alternative means which
cooperate with the composite lens so as to achieve apparently
neutral transmitted tint in the finished lens, when viewed in
daylight, be considered to be included within the scope of the
invention.
The photochromic front lens element of the preferred embodiment
darkens, becoming more brown in hue, thus absorbing more blue and
near-UV spectra as the intensity of the sunlight and its UV and
blue spectra increase, thereby compensating light level and
adjusting short-wavelength absorption simultaneously. The darkening
range of the photochromic element can be deliberately constrained
by controlling its exposure to UV wavelengths in the range of 360
to 400 nm through UV-absorbent coatings applied to its front
surface.
In one alternative embodiment, a photochromic lens element is used
which has a neutral-gray tint. The polarizing film has a brown
tint, while the other lens element is a trichroic contrast
enhancer. The relative contribution of the brown tint to the
overall color balance is maintained constant over light level
changes, as the neutral-gray photochromic element darkens in bright
sunlight to control light intensity without altering the
color-filtering properties of the lens.
In other alternative embodiments, no photochrornic lens elements
are used. Either one trichroic contrast enhancer lens element and
one crown-glass (tinted or clear) lens element, or two trichroic
contrast enhancer lens elements, are laminated together with a
polarizing film enclosed within. The dual-enhancer embodiments
produce stronger color and contrast enhancement. The transmitted
tint can bed neutralized or otherwise adjusted through additional
glass or polarizer tints, and/or mirror coatings as previously
described. As no photochromic element is used, the transmission
properties of this embodiment do not change when exposed to varying
levels of sunlight.
Conventional industry methods and processes for laminated glass
polarized lenses may be used, as such have been available
commercially for decades. Two lens elements of matching curvature
and appropriate thickness (typically around 1 mm) are ground and
polished, such that when laminated together with polarizing film
sandwiched within produce a composite lens with thickness and
weight similar to standard non-laminated glass lenses.
Corrective-prescription versions of the invention would have a
trichroic contrast enhancer as the front element with a clear crown
glass rear element to prevent unwanted center-to-edge density
gradients as would occur in high-diopter lenses.
The process used to fabricate a laminated plastic-lens embodiment
is similar to that described above for laminated glass lenses. Two
plastic lens elements are joined together with polarizing film
sandwiched within, to form a single lens. Alternatively, a plastic
lens of the invention may be molded or cast around the polarizing
film. Lastly, a molded plastic lens could have a polarizing
treatment applied externally. In the first case, the lens
"elements" are the two layers of plastic, one layer on each side of
the polarizer. In the last case, there is only one lens
element--that is, the entire molded lens body.
The trichroic filter scheme of the invention is realized in the
laminated plastic version by a means analogous to the glass-lens
embodiments. One or both of the plastic lens elements or layers--or
the polarizing film--is coated, dyed, or otherwise treated to
achieve the previously-defined trichroic spectral-transmission
properties, while any other treatments employed for overall
tint-neutralization are present in the same or other lens element
or layer, and/or in the polarizing film, and/or in surface
coatings. In a photochromic plastic lens of the invention, one of
the lens elements or layers is a photochromic plastic, while the
other is a trichroic contrast enhancer.
An uncoated lens can also be produced within the scope of the
invention. Tint-neutralization may be achieved in uncoated lenses
by using appropriate tints in the front element and polarizer. One
lens element of Schott S-8807 glass, a brown A polarizer, and one
green A lens element makes a good neutral-gray combination. Another
good combination is one lens element of Schott S-8801 glass, a
brown A polarizer, and clear crown glass for the second lens
element. Many other useful combinations are possible; these could
include the use of a photochromic front lens element. Referring to
FIG. 3, an uncoated embodiment is depicted as a composite lens body
generally designated 1 having a front lens element 2 and a rear
lens element 4, at least one of the lens elements being a trichroic
contrast enhancer, with the lens elements cojoined with and
enclosing a polarizing film 3.
As an alternative to laminated construction requiring two lens
elements, the invention may be realized in an embodiment wherein
the polarizer is applied to an external surface of a single lens
body. Such polarizing coating may be of the type disclosed by Keum
(U.S. Pat. No. 5,245,470), or it may be one of several other
methods known to those skilled in the art. Referring to FIG. 4, a
non-laminated lens generally designated 1 is formed of a single
lens body 10 which is a trichroic contrast enhancer, having a
polarizing coating or treatment 9 with a hydrophobic silicon or DLC
overcoating 6 applied to its convex surface, and having an
antireflectant coating 7 with a hydrophobic silicon overcoating 8
applied to its concave surface.
While the invention has been disclosed with reference to specific
embodiments, it is understood that variations may be made without
deviating from the essence of the invention.
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